Over the years, the developments of various synthetic yarns have made possible the production of various knit hosiery articles such as knit leotards, pantyhose, tights, knee-highs, ankle socks, leggings, stockings, and the like. These developments, however, have also resulted in many changes in the methods and procedures employed in the production, packaging, and marketing of the hosiery articles.
The production difficulties precipitated by the popularity of the stretch synthetic yarns used in the production of hosiery also have been further magnified by the increased popularity of pantyhose and other stockings in general. While the increased popularity has produced a need for increased automation in the production process and the accompanying reduction in cost, workable solutions to various problems have not been readily apparent and therefore have not been forthcoming.
In the manufacture of stretch pantyhose from synthetic yarns, for example, it is the conventional practice to knit the garment, either as a unitary structure (including the elastic waistband) or as separate components which are subsequently sewn together, from undyed yarns, and subsequently subjecting the undyed articles to shrinking and dyeing operations. The pantyhose therefore must be knitted, sewn, treated, inspected, transferred, and packaged in a manner that will not damage or unduly stretch the garment. The pantyhose is also preferably flattened and shaped to such a degree as to be easily packaged so that the pantyhose provides an acceptable quality level and an attractive appearance to the purchaser when removed from the package.
One area in the production process where problems have developed over the years in the production of hosiery articles such as pantyhose is in the knitting and sewing operations. For example, operational troubles may often occur during knitting or sewing which results in defects, i.e, picks, faulty or incomplete stitching, in the hosiery articles and thereby may considerably degrade the commercial value of the article. If the defective article reaches the market, it also may seriously blemish the reputation of the producer. Therefore, because these operations are imperfect, the knitted and/or sewn hosiery article is required to be inspected and graded prior to packaging and shipment to retailers and consumers.
Conventionally, the inspection of a completed hosiery article such as pantyhose has been done by visual human inspection of the completed article prior to packaging. This manual visual inspection process, however, is often tedious, time consuming, and includes a varying degree of human judgment even for similar quality standards. Even a certain batch of hosiery, for example, may have a wide variation of quality levels depending on the worker that inspected the completed article. Some operations also employ more than one worker in a particular line operation to inspect the completed hosiery article to ensure that an acceptable quality level is delivered to the retailers and consumers. Despite various inspecting tactics taken during the production process, the industry has been driven toward higher and more uniform production quality at a lower cost which manual labor often fails to provide.
Developments in the inspecting and grading process that have recently occurred have been targeted toward using video or charge coupled device ("CCD") cameras for inspecting a completed hosiery article. Examples of these video camera systems may be seen in European Published Application 0-529-621 titled "Machine For The Quality Control of Knit Products, In Particular Fine-Gauge Pantyhose, Knee Socks, Ankle Socks, And The Like, As Well As Method For The Visual Inspection Of Knit Goods," Japanese Published Application 60-065-173 titled "Fibrous Product Checking Apparatus With Computer Providing Pictorial Information Using Two Television Cameras," and the articles "The Automatic Inspection, Myth Or Reality" by Jean-Michel Yvain in DML Engineering and "Automated Garment Inspection Using Machine Vision" by L. Norton-Wayne in Leicester Polytechnic.
Because the conventional video camera failed to provide the resolution and magnification necessary to accurately inspect a hosiery article for many types of defects, the industry responded with hosiery inspection systems having high resolution video or CCD cameras which are capable of providing a detailed visual image of the hosiery article. These video and CCD cameras, however, are expensive and complex making them less attractive and not economically feasible to many producers of hosiery articles in the industry.